<style>
    iframe {
        width: 800px;
        height: 300px;
        position: absolute;
        top: -0px;
        left: -0px;
        z-index: 2;
        -moz-opacity: 0;
        opacity: 0;
        filter: alpha(opacity=0);
    }

    button {
        position: absolute;
        top: 281px;
        left: 323px;
        z-index: 1;
    }
</style>
<button>最新动态</button>
<img src="pic.jpg">
<iframe src="http://localhost:3000" scrolling="no"></iframe>